Re: [emergency-gis] Groups - Suggested changes for CAP 2.0 - CRS and GML (Best Practices for CRS - for OASIS.doc) uploaded

["Carl Reed OGC" <creed@opengeospatial.org>]

Art -

Thanks for the quick response to my posting. My answers are embedded below.

Cheers

Carl

PS: Sorry for the length of the response.

----- Original Message ----- 
From: "Art Botterell" <acb@incident.com>
To: <emergency-gis@lists.oasis-open.org>
Sent: Monday, January 31, 2005 2:17 PM
Subject: Re: [emergency-gis] Groups - Suggested changes for CAP 2.0 - CRS 
and GML (Best Practices for CRS - for OASIS.doc) uploaded


> Carl -
>
> With respect, I believe CAP is already recognized by the international 
> OASIS community as a truly international standard, and that any suggestion 
> to the contrary ought to be supported by evidence.
>

Not to split hairs - and please correct me if I am wrong - but as far as I 
know, OASIS is not an accredited Standards Developing Organization (SDO). 
Before the flames start, neither is the OGC :-) As the OASIS by-laws state, 
OASIS is a Consortium. The OGC is also a Consortium. ISO is an SDO. 
Therefore, technically, both the OGC and OASIS develop specifications and 
not formal international standards. ISO, the IEC, and others like them 
develop standards. This is one reason many of the OGC specs are submitted to 
ISO. They go through the very formal ISO process in order to be recognized 
as true international standards. This may all be nit-picky legalize, but 
under circular A-119, there is something call a Voluntary Consensus 
Standards Organization. If a consortium meets a number of criteria and can 
prove this to NIST/ANSI, then the consortium has the legal right to call 
themselves a standards organization that develops international standards. 
The OGC is going through this accreditation process now.

All that said, there is the ability for creation of de-facto standards. If a 
majority of EM application implementers decide to use CAP, then it will 
become a de-facto standard.

> And while I have no objection to considering extensions to CAP, I think 
> they should be driven by specific stated requirements.  It would help me 
> if you could summarize what specific problems we need to solve here.

Very simple. In the the geospatial technology world (remote sensing, sensor 
webs, location services, GIS, CAD and the list goes on), integration of 
content from many sources, including alerts, is a paramount requirement of 
many applications. The concepts of fusion, sharing, and integration requires 
that proper metadata and content be available. The OGC members are getting 
ready to start an interoperability experiment in which CAP will be used. 
They will be evaluating CAP from the perspectives that I just mentioned.

Anyway, these are the same change requests I have been making on behalf of 
the OGC membership for the last 18 months. So at least I am being consistent 
:-)

> In particular, what would be the practical benefit of supporting multiple 
> reference systems in addition to WGS-84?  Wouldn't it be more efficient to 
> have any coordinate conversions done once-and-for-all by the originators 
> than to have them duplicated, perhaps thousands of times and potentially 
> with differing outcomes, by the various receivers?  And if we have the 
> WGS-84 representations, what's the value of duplicating that information?

You miss the point. I am not suggesting that CAP physically support numerous 
CRS's. I am saying why not have the ability to support any CRS with WGS as a 
default. This provides much greater implementation flexibility and future 
proofs CAP from either existing or future changes in legal and policy 
requirements on a nation by nation basis.

So, let's consider some countries other than the US and what they use for 
their legal national mapping programs. This is not to say that implementors 
could not use WGS 84, but there would be pressure to use something else.

Poland:  Ellipsoid: Krassowskij; Official Map Projections:  Quasi 
Stereographic (Roussilhe 1922) for Zone 1-4  Gauß-Krüger for Zone 5, Central 
Point/Datum: Pulkowo/System 1942.

Australia: The Geocentric Datum of Australia (GDA) is a coordinate reference 
system that best fits the shape of the earth as a whole. It has an origin 
that coincides with the centre of mass of the earth, hence the term 
"geocentric". Following a resolution of the Intergovernmental Committee on 
Surveying and Mapping (ICSM) in 1988, it is being progressively implemented 
throughout Australia as the preferred datum for all spatial information.

Thailand: WGS 84 (a recent move as their new geodetic network is tied into 
GPS).

As you can see, there is great variety. If you go to www.safe.com, they have 
a partial list of datums in use by many different countries. Many of these 
are the legal datums for the country and are used for such purposes as 
developing an integrated multipurpose cadastre.

> Not opposed to enhancements per se, but I hope we can guard against 
> creeping featuritis by making sure any additions actually represent a 
> cost/benefit improvement for the implementers.  We've seen so many good 
> products become bloated by a series of well-intentioned WIBNI ("wouldn't 
> it be nice if") feature-extensions...

I whole heartedly agree - I coach OGC members to this reality all the time. 
Simple is better as it makes implementation easier. However, by adding a few 
optional elements, then CAP becomes a much richer messaging protocol that 
can provide much more content and context if the application developer so 
desires.

> - Art
>
>
> At 7:03 PM +0000 1/31/05, creed@opengeospatial.org wrote:
>>RE: Suggested Change Requests for CAP 2.0
>>
>>  -- Dr Carl Reed
>>
>>The document named Suggested changes for CAP 2.0 - CRS and GML (Best
>>Practices for CRS - for OASIS.doc) has been submitted by Dr Carl Reed to
>>the EM GIS SC document repository.
>>
>>Document Description:
>>If CAP is to be considered by the international community as a truly
>>international standard, then both normative and informational narrative
>>will need to added to the document. Much of this has to do with observing
>>existing international best practices and standards for dealing with
>>geospatial content  including coordinate reference systems and geometry
>>(areas). However, at the same time we do not wish to harm the simplicity
>>of implementation of the current specification nor do we wish to break
>>backwards compatibility.
>>
>>Therefore, the following is recommended for discussion as change requests
>>for CAP 2.0.
>>
>>
>>Download Document:
>>http://www.oasis-open.org/apps/org/workgroup/emergency-gis/download.php/11254/Best%20Practices%20for%20CRS%20-%20for%20OASIS.doc
>>
>>View Document Details:
>>http://www.oasis-open.org/apps/org/workgroup/emergency-gis/document.php?document_id=11254
>>
>>
>>PLEASE NOTE:  If the above links do not work for you, your email 
>>application
>>may be breaking the link into two pieces.  You may be able to copy and 
>>paste
>>the entire link address into the address field of your web browser.
>>
>>-OASIS Open Administration
>
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